The present invention relates to prefabricated structural elements, especially cantilevered elements suitable for constructing a balcony or the like. It is known to employ for the construction of balconies prefabricated panels or slabs. Such a balcony panel or slab and the respective floor slab have initially a thickness which is smaller than the thickness of the finished balcony or the finished floor. The structural assembly is accomplished by resting the balcony slab with one side on the supporting wall to abut the adjacent floor slab. The opposite side facing away from the floor slab and away from the wall is initially supported by means which are later removed. After placing the balcony slab in the just described manner, reinforcing rods are applied to the balcony slab and to the floor slab, whereupon poured-in-place concrete is applied over the balcony slab and over the floor slab, whereby the reinforcing rods are embedded and the balcony portion is interconnected with the adjacent floor slab. The above mentioned supporting means may only be removed after the poured-in-place concrete has sufficiently hardened. Only after such hardening is it possible to place loads on the balcony.
The above described conventional method of constructing balconies has several disadvantages. One such disadvantage is seen in that the above mentioned additional supporting means are required. Another drawback is seen in the time required for the hardening of the reinforced poured-in-place concrete. A still further drawback is seen in that the unitary structure formed from the balcony slab and the floor slab rigidly interconnected with each other by the reinforced poured-in-place concrete form a unitary plate which rests on the supporting wall or header without contributing to the load carrying capacity of the header. As a result, the height of the header, which may be taken into consideration in calculating the structural strength, is only that portion reaching to the bottom surface of the floor slab. Thus, in order to provide for the necessary supporting strength, the header must comprise additionally a double T-supporting girder.